Mr Simpson, 40, struggled severely with altitude sickness during the seven-day walk but reached the summit nonetheless with the others on February 18.

He said: “Climbing Kilimanjaro is by far the most physically demanding challenge I have ever undertaken. The thing is, it’s not just a long walk - you can’t breathe. There’s no oxygen so that’s the killer for people.”

The group trekked for four days to get to Barafu High Camp, then set out to walk through the night to reach the summit at dawn before a 19-hour descent.

Mr Simpson said: “It’s most punishing when you get to the top. As you come down you improve but it took me a while to readjust so it was quite a long walk down.

“It’s hard to explain, but at that altitude to walk up half a dozen steps would just take every ounce of energy that you have.”

But Mr Simpson said he was “determined” to reach the summit along with the “amazing” group.

He said Daisy Chain, which addresses the needs of children who are on the autistic spectrum and supports their families, will benefit through social club activities for youngsters.

He said to put on a two-hour social club costs around £300.

Receiving no formal funding, the charity relies on the support of business and the community.

It has suffered a 30% reduction in income, but Mr Simpson said things are picking up. He added: “We hope that the group’s amazing achievement will inspire other people to put on their walking boots and take part in either our 2013 Kilimanjaro walk or one of our other expeditions.”

Daisy Chain also runs fundraising expeditions to Cotopaxi in Ecuador, the world’s largest active volcano, and the renowned Inca Trail in Peru, which finishes at Machu Picchu.